[GHC] #11982: Typechecking fails for parallel monad comprehensions with polymorphic let

[GHC]

#11982: Typechecking fails for parallel monad comprehensions with polymorphic let
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        Reporter:  simonpj           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 Yes the ''output'' of typechecking is impredicative, but the input is not,
 and plainly should not be rejected.  But we may not want to just "enable
 impredicativity" because that ma allow too much.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11982#comment:3>
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